Vertically lifted portable electric furnace and method for use thereof

ABSTRACT

A method and apparatus for heating a metallic material held by a holder such as a crucible which is positioned on a base using an electric furnace. The electric furnace includes a sleeve, an electric heating element disposed on the inner surface of the sleeve, a removable lid for covering a top opening of the sleeve and at least one handle disposed on the outer surface of the sleeve for lifting and removing the sleeve from the base or placing the sleeve on the base. When the sleeve is placed on the base enclosing the crucible, the removable lid is placed on the top opening of the sleeve and an electric current is applied to the electric heating element. Heat generated by the electric heating element and retained in the furnace melts the material contained in the crucible.

This is a continuation of application Ser. No. 08/459,132, filed Jun. 2,1995, now U.S. Pat. No. 5,585,023; which is a continuation ofapplication Ser. No. 08/267,401, filed Jun. 29, 1994, now U.S. Pat. No.5,539,183.

BACKGROUND OF THE INVENTION

The present invention relates to a furnace, for heating and ultimatelymelting a material at high temperatures. More particularly, the presentinvention relates to an easy to use and portable electric furnace havinghandles to permit the furnace to be vertically lifted and moved about.The furnace is lifted from the base once the metallic material has beenmelted thereby reducing unnecessary handling of the melted metallicmaterial. The molten metal is only handled once.

Small metal castings, such as those made by hobbyist, artist orprofessionals using, for example, five pounds or more of material,heretofore have been difficult or expensive to make. Further, extremesafety risks are created in the handling of the melted material,particularly when casting materials having high melting temperaturessuch as bronze. Bronze has a melting point of 2000° fahrenheit.

Currently in order for hobbyist, artist or professionals to cast a metalobject the object must be relatively small using small amounts ofmaterial and/or made of a material having a low melting point such asgold. Satisfying such constraints permits the use of small heaters suchas those used by jewelers, small part makers, etc.

Small heaters used by jewelers satisfy the requirement of portabilitybeing that they can be moved and used in almost any setting and requirestandard household electricity to operate. However, such heaters sufferfrom various disadvantages. Namely the heaters can only melt smallquantities of metallic material. Further, the heaters cannot be used tomelt, for example, a pound or more of material used to cast works ofart, machine parts or tools. In order for the hobbyist, artist or even aprofessional to cast small metal objects using approximately a pound ormore of material larger furnaces, such as those owned by foundries, areused. Foundries typically use fuel fired furnaces. A fuel fired furnace210 as illustrated in FIG. 2A has a cylindrical opening 212 forreceiving a crucible 214 containing the material to be melted. The fuelfired furnace 210 also includes gas jets 216 that when lit applies aflame to the inside of the opening 212. The heat generated by the flamecauses the metallic material contained in the crucible 214 to reach itsmelting point.

The above-described fuel fired furnace 210 suffers from variousdisadvantages. One disadvantage is that the fuel fired furnace 210 isnot portable and can only be operated by professionals. Another mostimportant disadvantage is that the melted material must be handled atleast two times prior to casting.

Due to the construction of the fuel fired furnace 210 the cruciblecontaining the metallic material must be vertically lowered into andlifted out of the opening 212 of the furnace by lifting tongs 218 asillustrated in FIG. 2B. The lifting tongs 218 are manipulated by twooperators, one at either end of the lifting tongs 218. The two operatorsby manipulating the lifting tongs 218 causes the fingers 220 of thelifting tongs 218 to clamp about the crucible 214. The crucible 214 isthen lifted out of the opening 212 of the furnace 210 in the verticaldirection. Once the crucible 214 containing the melted material has beenlifted out of the opening 212 of the furnace 210, the crucible 214 isthen placed on the floor of the foundry within a pouring ring 222 ofpouring tongs 224 as illustrated in FIGS. 2C and 2D. The pouring tongs224 have a pouring finger 226 which clamps over the lip of the crucible214 to prevent the crucible 214 from slipping out of the pouring ring222 during pouring. Two operators are also necessary for manipulatingthe pouring tongs 224. One of the operators acts as a fulcrum while theother operator acts as the controller. The controller tilts the crucible214 to control the pouring of the melted material by use of thehandlebars 226.

Thus, the crucible containing the melted material is handled a firsttime when the crucible is lifted from the opening of the furnace andplaced on the floor of the foundry using lifting tongs and a second timewhen the crucible is lifted from the floor of the foundry and the meltedmaterial is poured into the mold using the pouring tongs. Handling amelted material at temperatures sometimes as high as 2000° fahrenheitcan be extremely dangerous for the professional as well as thenon-professional such as hobbyist and artist. Injury to the operator ordamage to the surrounding area may occur.

Therefore, for professionals and particularly non-professionals there isa need to provide a furnace that is portable and easy to use and thatreduces the number of times the melted material is handled.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an electric furnace forheating and melting materials at high temperatures that is portable andeasy to use.

Another object of the present invention is to provide an electricfurnace for heating and melting approximately five pounds or more ofmaterial at a high temperature within a reasonable time to cast smalland medium sized objects.

Yet another further object of the present invention is to provide anelectric furnace for heating and melting a material at high temperaturesthat reduces unnecessary handling of the heated or melted material.

The present invention provides a portable and easy to use electricfurnace for heating and melting a metallic material held by a holdersuch as a crucible which is positioned on a base. The electric furnaceof the present invention includes a sleeve, that may be cylindrical inshape and has a hollow opening that extends its entire length.

The electric furnace of the present invention also includes an electricheating element disposed within the inner surface of the sleeve, aremovable lid for covering a top opening of the sleeve and at least onehandle disposed on the outer surface of the sleeve. The handle permitsthe sleeve to be vertically lifted by a user to remove the sleeve fromor place the sleeve on the base. The handle is also used to move thefurnace from one location to the next. The removable lid allows the userto monitor the status of the material being heated, add more material asneeded and perform operations to aid in the melting process such as addflux or remove slag. The removable lid also allows the user to view theholder during lifting of the sleeve. The furnace is relative small instructure permitting the furnace to be set up in a small area and thefurnace operates using standard household current.

The electric furnace is operated by placing the sleeve on the base withthe hollow opening of the sleeve being positioned around the crucible.The removable lid is placed on the top opening of the sleeve. Theremovable lid, the inner surface of the sleeve and the base forms aheating chamber for heating the material contained in the crucible. Thematerial contained in the crucible is heated and ultimately melted whenstandard household electric current is applied to the electric heatingelement.

The removable lid may be pivotally mounted on the top surface of thesleeve. Also the sleeve may be formed as a heating unit with an openbottom, a closed top and an opening formed with the heating unitcommunication with the open bottom. Thus, the need for a lid iseliminated and a window may be provided at the closed top to permit theuser to monitor the status of the material being melted.

BRIEF DESCRIPTION OF THE DRAWINGS

The improvements of the present invention and the advantages resultingtherefrom will become apparent upon reading the following description ofthe preferred embodiments in light of the drawings in which like partsare designated with like numerals and in which:

FIG. 1A illustrates an electric furnace of the present invention;

FIG. 1B illustrates another embodiment of the sleeve of the electricfurnace of the present invention;

FIGS. 2A-D illustrate a conventional fuel fired furnace and conventionalcasting apparatus;

FIG. 3 illustrates a sectioned view of the sleeve of the presentinvention;

FIG. 4 illustrates a removable lid of the present invention;

FIG. 5 illustrates crucible of the present invention;

FIG. 6 illustrates a base of the present invention; and

FIG. 7 is a flowchart of the steps of heating a metallic material usingthe electric furnace of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an electric furnace for heating andmelting a metallic material held by a hold such as a crucible which ispositioned on a base. The electric furnace of the present invention iseasy to use, portable and reduces unnecessary handling of the molten orheated material by the user. The electric furnace of the presentinvention accomplishes this by providing handles on the outer surface ofthe furnace and an opening in the bottom surface of the furnacepermitting the user to vertically lift the electric furnace up and awayfrom the base thereby exposing the crucible. The user can then grab thecrucible using tongs and pour the melted material into a mold. Thus, theelectric furnace of the present invention only requires the user tohandle the melted material when the melted material is ready to bepoured into the mold. Further, the electric furnace of the presentinvention can be easily moved from one location to the next using thehandles and can be set up and operated in a small area due to itsrelatively small structure. Also the electric furnace of the presentinvention can be operated using standard household electric current.

The electric furnace of the present invention, as illustrated in FIG. 1Aincludes a sleeve 100 having inner and outer surfaces and a hollowopening 102 formed by the inner surface that extends the entire lengthof the sleeve 100. The sleeve 100 has a continuous helical groove 104formed in the inner surface of the sleeve 100. The helical groove 104has an electric heating element 106 disposed therein. The electricheating element 106 is connected to conductors 108 which are connectedto connectors 110 attached to the outer surface of the sleeve 100. Theconnectors 110 permit ground and voltage potentials to be applied to theelectric heating element 106. Applying ground and voltage potentials toconnectors 110 causes an electric current to flow through the electricheating element 106 thereby generating heat.

The electric furnace of the present invention also includes a removablelid 112 and a base 114 for covering top and bottom openings of thesleeve 100. The removable lid 112 has handles 116 for use by the user tolift the removable lid 112 from the top opening of the sleeve 100. Theremovable lid allows the user to monitor the status of the materialbeing heated, add more material as needed and perform operations to aidin the melting process such as add flux or remove slag. The removablelid also allows the user to view the holder during lifting of thesleeve. The base 114 provides a surface upon which the sleeve 100 rests.

The outer surface of the sleeve 100 has handles 118 disposed thereon orintegral therewith that permit the sleeve to be vertically lifted andremoved from or placed on the base 114. As described above, the sleeve100 is not physically attached to the base 114. A crucible 120 ispositioned on the base 114 and holds the metallic material to be heatedor melted.

Another embodiment of the sleeve is illustrated in FIG. 1B. The sleeveof the other embodiment is formed as a heating unit 122 as illustratedin FIG. 1B. The heating unit 122 is formed in the same manner as thesleeve described above, with respect to FIG. 1A, except that the heatingunit 122 eliminates the need for the removable lid 112. The heating unit122 as illustrated in FIG. 1B has an open bottom and a closed top and achamber 123 formed within the heating unit that communicates with theopen bottom. A window 124 is provided at the closed top to permit theuser to monitor the status of the material being heated.

FIG. 3 illustrates a section view of the sleeve 100. The sleeve 100, asillustrated in FIG. 3 has an outer layer 300 made of a metallic materialand an inner layer 302 made of a refractory or ceramic type materialwhich can withstand high temperatures. Insulative material or an airspace 301 may be provided between the outer layer 300 and the innerlayer 302 so as to insulate the outer layer 300 from the hightemperatures generated within the sleeve. Providing an insulativematerial or an air space between the outer layer 300 and the inner layer302 causes the outer layer 300 to remain at relatively low temperaturespermitting the user to contact the outer surface of the sleeve 100 evenwhen the furnace is being operated.

Grooves 104 are formed in the inner surface of the sleeve 100. Thegrooves may be formed by machining or by molding refractory or ceramicmaterial about a rubber hose helically wound over a mandril. The rubberhose is either removed or is burned off during the hardening processthereby leaving a groove in the inner surface of the sleeve 100. Therefractory or ceramic material may also be molded about the electricheating element 106.

FIG. 4 illustrates a section view of the removable lid 112. Theremovable lid 112, like the sleeve 100 illustrated in FIG. 3, includesan outer layer 400 made of a metallic material and an inner layer 402formed of a refractory or ceramic type material which can withstand hightemperatures. Also the removable lid 112 includes handles 116. Theremovable lid 112, as illustrated in FIG. 4, includes a stopper portion404 which causes the removable lid 112 to snugly fit within the topopening of the sleeve 100. The removable lid 112 may also be pivotallyattached to the top surface of the sleeve 100 by a hinge 406. One end ofthe hinge 406 being attached to the removable lid 112 as illustrated inFIG. 4 and the other end of the hinge 406 being attached to an uppermostpart of the outer surface of the sleeve 100 near the top opening of thesleeve 100.

Insulative material or an air space may be provided between the outerlayer 400 and the inner layer 402 of the removable lid 112 to insulatethe outer layer 400 from the high temperatures generated within thefurnace. Thus, the outer surface of the removable lid 112 may be touchedby the user even during operation of the furnace.

FIG. 5 illustrates the crucible 120 of the present invention. Thecrucible includes a cup 500 for holding the material to be melted and aspout 502 used for pouring the melted material. The crucible 120 alsoincludes a crucible base 504 having a relatively large foot forstability.

FIG. 6 illustrates the base 114 of the present invention. The base 114is made of fire resistant brick or other material. The base includes aconcentric groove 600 formed in the top surface of the base 114 forreceiving the sleeve 100. The base 114 also includes a center landingarea 602 for receiving the crucible base 504.

When the sleeve 100 is placed in the concentric groove 600 of the base114 and the stopper portion 404 of the removable lid 112 is fittedsnugly into the top opening of the sleeve 100, a heating chamber isformed by the top surface of the base 114, the inner surface 102 of thesleeve 100 and the stopper portion 404 of the removable lid 112. When anelectric current is applied to the electric heating element 106, heat isgenerated by the electric heating element 106 and retained in theheating chamber. The heat retained in the heating chamber heats andultimately melts the material held by the crucible 120 which has beenpositioned on the landing area 602 of the base 114.

In order to heat or melt metallic material in the electric furnace ofthe present invention the following steps, as illustrated in FIG. 7 areperformed:

Step 701: The sleeve 100 is vertically lifted by handles 118 away fromthe base 114 and placed on the floor beside the base.

Step 702: Metallic material to be melted is placed on the crucible 120and the crucible is positioned on the base 114.

Step 703: The sleeve is vertically lifted by handles 118 and placed onthe base 114 enclosing the crucible 120.

Step 704: The removable lid 112 is placed on the top opening of thesleeve 100.

Step 705: Electric power is applied to the connectors 110 to cause anelectric current to flow through the electric heating element 106thereby generating heat.

Step 706: The state of the metallic material contained in the crucible120 is monitored by vertically lifting the removable lid 112 from thetop opening of the sleeve 100 using the handles 116. Flux may be addedto or slag may be removed from the material contained in the cruciblethrough the top opening of the sleeve 100 when the lid is removed.

Step 707: Once the metallic material has completely melted the sleeve isvertically lifted and removed from the base using handles 118 and placedon the floor beside the base 114.

Step 708: Tongs are used to grab the crucible 120 and pour the meltedmaterial into the mold.

There has been described a new and useful electric furnace havingapparatus for reducing unnecessary handling of the melted material. Itshould be appreciated that modifications and additions will be apparentto those of ordinary skill in the art in applying the teachings of theinvention described herein to various applications. Accordingly, theinvention should not be limited by the description herein of thepreferred embodiments but rather the invention should be construed inaccordance with the following claims.

I claim:
 1. A method of heating a material being held by a holderpositioned on a base using an electric furnace which includes a sleevefor enclosing the holder positioned on the base, an electric heatingelement disposed on the inner surface of said sleeve, a removable lidfor covering a top opening of said sleeve, and at least one handledisposed on the outer surface of said sleeve, said method comprising thesteps of:placing said sleeve including said removable lid, using said atleast one handle, on the base enclosing the holder; applying an electriccurrent to said electric heating element, thereby generating heat whichis retained in said electric furnace to heat the material held in theholder; and removing said sleeve including said removable lid from saidbase by lifting said sleeve using said at least one handle after thematerial held in the holder has been heated.
 2. A method according toclaim 1 wherein said sleeve includes an outer layer and an inner layer.3. A method according to claim 2 wherein said outer layer is made of ametallic material and said inner layer is made of a refractory material.4. A method according to claim 2 wherein said outer layer is made of ametallic material and said inner layer is made of a ceramic material. 5.A method according to claim 2 wherein an insulative material is providedbetween said outer layer and said inner layer.
 6. A method according toclaim 2 wherein an air space is provided between said outer layer andsaid inner layer.
 7. A method according to claim 1 wherein saidremovable lid is pivotally attached to an uppermost part of the outersurface of said sleeve.
 8. A method according to claim 1 wherein ahelical groove is formed in the inner surface of said sleeve and saidelectric heating element is disposed in said helical groove.
 9. A methodaccording to claim 1 wherein said removable lid comprises an outer layerand an inner layer.
 10. A method according to claim 9 wherein said outerlayer is formed of a metallic material and said inner layer is formed ofa refractory material.
 11. A method according to claim 9 wherein saidouter layer is formed of a metallic material and said inner layer isformed of a refractory material.
 12. A method according to claim 1wherein said at least one handle is formed integrally with the outersurface of said sleeve.
 13. A method according to claim 1 wherein saidheat generated by said electric heating element is sufficient to meltthe material held in the holder.
 14. A method of heating a material heldby a holder positioned on a base using an electric furnace whichincludes a heating unit having an open end and a closed end wherein theopen end communicates with a chamber formed within said heating unit, anelectric heating element disposed on the surface of said chamber formedwithin said heating unit, and at least one handle disposed on the outersurface of said heating unit, said method comprising the stepsof:placing said heating unit, using said at least one handle, on thebase enclosing the holder within said chamber; applying an electriccurrent to said heating element, thereby generating heat which isretained in said chamber to heat the material held by the holder; andremoving said heating unit from said base by lifting said heating unitusing said at least one handle after the material held in the holder hasbeen heated, wherein said closed end of said heating unit includes awindow which permits a user to monitor conditions of said material. 15.A method according to claim 14 wherein said heating unit includes anouter layer and an inner layer.
 16. A method according to claim 15wherein said outer layer is formed of a metallic material and said innerlayer is formed of a refractory material.
 17. A method according toclaim 15, wherein said outer layer is formed of a metallic material andsaid inner layer is formed of a ceramic material.
 18. A method accordingto claim 14 wherein said at least one handle is formed integrally withthe outer surface of said heating unit.
 19. A method according to claim14 wherein said heat generated by said electric heating element issufficient to melt the material held by the holder.
 20. A methodaccording to claim 14, wherein said chamber is closable.